1. FIELD OF THE INVENTION
The present invention relates generally to fluid flow control valves of the type wherein a valve plug and a valve seat are brought into fluid-tight sealing engagement through an eccentric rotary or swinging movement of the plug. Specifically, the invention relates to the construction of the seats of such eccentric rotary valves to the end of facilitating the consistent attainment of the desired movement and fluid-tight sealing engagement between the plug and its cooperating seat.
2. DESCRIPTION OF THE PRIOR ART
Many different forms of seats for rotary valves of the type identified above are known in the art. One of the more popular forms of such seats are the rigid and rigidly mounted seats which are employed in rotary valves of the type having either a flexible actuating arm for the plug or having a flexible connection between the plug and a rigid actuating arm. An example of a rotary valve with such a rigid seat and flexible actuating arm for the plug is found in the Baumann U.S. Pat. No. 3,623,696. An example of a rotary valve having a rigid seat and a plug which is flexibly or shiftably mounted on a rigid arm is found in the Myers U.S. Pat. No. 3,963,211.
Another known form of the type of valves identified above is the form wherein a rigid seat is moveable as a unit within the valve housing to facilitate the obtaining of the desired sealing engagement between the plug and the seat. Examples of this form of seat and valve are found in the Allen U.S. Pat. No. 3,191,619 and in the Sutter et al U.S. Pat. No. 3,946,986.
Still another known form of valves of the above-identified type is that in which the seat has flexible lips against which the plug seals when in its valve-closed position. An example of this type of valve and seat is found in the Vulliez French Patent No. 1,282,630. Another example of a lipped seat in an eccentric rotary valve is found in the Rihm et al U.S. Pat. No. 4,073,473.
Additionally, it has been proposed in Japanese Patent Application No. 105,758/76, filed on Sept. 6, 1976, to provide a unitary seat member for eccentric rotary valves which is characterized by having annular base and rigid annular seating portions connected by a funnel-shaped resilient portion with its smaller internal or inner diameter located at the base portion and its larger inner diameter located at the seating portion. The resilient connecting portion of such a seat construction is intended to permit the seating portion to shift into proper sealing engagement with the moving plug.
Although the forms of valves and valve seats referred to above have doubtless found utility in numerous applications, each of the known constructions as described above possesses a shortcoming which has kept it from being entirely suitable. For example, in the form of valve having a rigid seat and a flexible plug actuating arm, undesirable wear is experienced because the plug must slide over the edge of the cooperating seat as the plug is forced into the closed position. The form of valve having a flexibly mounted plug has the disadvantage of requiring a complex structure to achieve the needed flexibility, and also has the disadvantage of being subject to plug instability and flutter.
The form of rigid seat which is moveable as a unit within the valve housing has presented problems resulting from the need for fluid-tight sealing between the moving seat unit and the valve body, and resulting from the inherently complex construction of such a moveable seat unit. The flexible lip type of seat suffers from such problems as wear, erosion, and/or permanent deformation into a poor sealing condition, and the inability to withstand high fluid velocities. Finally, the form of valve employing the noted unitary seat member with the funnel-shaped connecting portion is subject to sticking or jamming of the plug on the seating portion, thus presenting problems in connection with the moving of the plug off of the seating portion.